Implantable prosthetic valve assembly and method for making the same

ABSTRACT

An implantable prosthetic valve assembly having a support stent, or frame, having circumferential struts with multiple bends forming obtuse angles when the valve assembly is expanded to its functional size. The frame can be manufactured with one or more of the circumferential struts in a partially collapsed state and a flexible valve member can be mounted to the partially collapsed frame. The partially collapsed struts can be formed with multiple bends having angles selected to facilitate crimping of the frame to a profile suitable for percutaneous delivery. When the frame is expanded, the bends can expand to form obtuse angles, thereby enhancing the rigidity of the frame to better resist closing forces exerted on the valve assembly.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.11/644,517, filed Dec. 22, 2006, now U.S. Pat. No. 8,236,045.

FIELD

The present disclosure concerns embodiments of an implantable prostheticvalve and method for making the same.

BACKGROUND

Prosthetic cardiac valves have been used for many years to treat cardiacvalvular disorders. The native heart valves (such as the aortic,pulmonary and mitral valves) serve critical functions in assuring theforward flow of an adequate supply of blood through the cardiovascularsystem. These heart valves can be rendered less effective by congenital,inflammatory or infectious conditions. Such damage to the valves canresult in serious cardiovascular compromise and even death. For manyyears, the definitive treatment for such disorders was the surgicalrepair or replacement of the valve during open heart surgery, but suchsurgeries are prone to many complications. More recently, atransvascular technique has been developed for introducing andimplanting a prosthetic heart valve using a flexible catheter in amanner that is less invasive than open heart surgery.

In this technique, a prosthetic heart valve is mounted in a crimpedstate on the end portion of a flexible catheter and advanced through ablood vessel of the patient until the valve reaches the implantationsite. The valve at the catheter tip is then expanded to its functionalsize at the site of the defective native valve such as by inflating aballoon on which the valve is mounted.

FIG. 1 shows a known percutaneous heart valve 10 in its deployed orexpanded state. The valve 10 comprises a flexible prosthetic valvemember 12 attached to an expandable frame, or support stent, 14 withsutures 16. The frame 14 includes angularly-spaced, axial struts 18 andcircumferentially extending, zig-zag struts 20 secured to the axialstruts 18. Between each pair of axial struts 18, each strut 20 comprisestwo linear strut members 22 a, 22 b forming a bend in the strut tofacilitate crimping of the valve 10 to a smaller diameter forpercutaneous delivery of the valve. As can be appreciated, the easiestand most straightforward way of attaching the valve member 12 to theframe 14 is when both the frame 14 and the valve member 12 are in theexpanded state shown in FIG. 1. The assembled valve 10 typically isstored in the expanded state or a partially crimped state and then fullycrimped to a much smaller profile in the operating room just prior toimplantation.

An important characteristic of a percutaneous prosthetic heart valve isits ability to be crimped to as small diameter as possible to permit thecrimped valve to be advanced through the blood vessels to animplantation site. Another important characteristic of a percutaneousheart valve is its ability to retain an expanded shape once implanted.To maximize circumferential and radial rigidity of the valve frame, andtherefore enhance the ability of the frame to retain an expanded shapeonce implanted, it is desirable to maximize the angle θ between strutmembers 22 a, 22 b. Ideally, the struts 20 should be nearly circular(i.e., the angles θ are slightly less than 180 degrees) to providemaximum rigidity. Moreover, by increasing the rigidity of the struts,less metal can be used for forming the frame, which allows the valve tobe crimped to a smaller profile.

Unfortunately, forming the struts 20 with angles θ that are greater than90 degrees can lead to uneven and unpredictable crimping. Thus, if thevalve assembly is assembled in its expanded, functional shape, then inorder to permit even and predictable crimping of the frame to apredetermined profile suitable for percutaneous delivery, rigid strutswith obtuse angles θ cannot be utilized.

SUMMARY

In one aspect, the present disclosure concerns an implantable prostheticvalve assembly having a support stent, or frame, having circumferentialstruts with multiple bends forming obtuse angles when the valve assemblyis expanded to its functional size. The frame can be manufactured withone or more of the circumferential struts in a partially collapsed stateand a flexible valve member can be mounted to the partially collapsedframe. The partially collapsed struts can be formed with multiple bendshaving angles selected to facilitate crimping of the frame to a profilesuitable for percutaneous delivery. When the frame is expanded, thebends can expand to form obtuse angles, thereby enhancing the rigidityof the frame to better resist closing forces exerted on the valveassembly (for example, the recoil force exerted on the frame by thedistorted stenosed native valve orifice). In particular embodiments, thebends of at least some of the struts when expanded form obtuse anglesthat are at least about 120 degrees or greater.

In an exemplary embodiment, the frame is manufactured in a partiallycollapsed state having a generally tubular shape, and a valve member,such as a tricuspid valve member, is attached to the partially collapsedframe. The partially collapsed frame has plural, axial spacedcircumferential struts formed with multiple bends that have anglesselected to facilitate crimping of the valve assembly to a smallerdiameter and that expand to obtuse angles when the valve member isexpanded to its functional size. In certain embodiments, for example,the partially collapsed frame is formed with bends having acute anglesand expanding the frame forms bends that are at least about 120 degrees.The frame desirably can be crimped to a diameter of about 24 French orless for delivery through a patient's vasculature on a catheter orequivalent mechanism.

When the valve member is mounted to the partially collapsed frame, thediameter of the valve member is greater than the diameter of thepartially collapsed frame. For instance, in certain implementations, thediameter of the valve member is twice that of the partially collapsedframe. The valve member therefore cannot conform to the shape of thepartially collapsed frame, and as a result, assembly of the valveassembly is rendered more difficult. Various techniques therefore can beutilized to ensure that the valve member is connected to the frame in amanner that when the frame is expanded, the valve member can assume itsfunctional shape.

In one approach, a flexible skirt is used as an aid for mounting thevalve member. The skirt has visual indicia marking the locations alongthe length of the skirt for attaching the skirt to the inner surface ofthe frame. Such visual indicia can be for example, markings on thesurface of the skirt, slits or apertures, sutures attached to the skirt,or a longitudinal edge of the skirt shaped to indicate the attachmentlocations. The skirt is first attached to the inner surface of the frameand then the valve member is attached to the inner surface of the skirt.The skirt and the valve member are connected to the frame such that whenthe valve assembly is expanded, the skirt and the portion of the valvemember attached to the skirt substantially conform to the shape of theexpanded frame.

In another approach, a folding device is used to fold or bend the valvemember into an undulated shape having a diameter that is approximatelyequal to the diameter of the partially collapsed frame. In use, thevalve member is placed in the folding device and is folded to a smallerdiameter. The frame is placed around the folded valve member, which isthen attached to the frame at the apexes of the folds contacting theframe. In another implementation, both the valve member and the skirtare placed in the folding device and folded to a smaller diameter. Theframe is then placed around the folded skirt and valve member, which arethen attached to the frame. In another implementation, the foldingdevice can be used to fold the skirt, which is then attached to theframe. The partially assembled valve is then removed from the foldingdevice and the valve member is mounted to the frame.

In one representative embodiment, a method is provided for assembling animplantable prosthetic valve comprising a crimpable frame and valvemember. The method comprises connecting the valve member to an innersurface of the frame member while a portion of the frame is at leastpartially crimped, with the partially crimped frame portion having adiameter that is less than the diameter of the valve member when thevalve member is expanded to its functional size.

In another representative embodiment, a method of assembling animplantable prosthetic valve assembly comprises forming an annular framein a partially crimped state, and mounting a flexible valve member to aninner surface of the partially crimped frame having a diameter that isless than the diameter of the valve member when expanded to itsfunctional size.

In another representative embodiment, a method of percutaneous heartvalve replacement comprises assembling a heart valve assembly byconnecting a valve member to an expandable support stent when the stentis in a partially collapsed state having a first diameter. The methodfurther comprises storing the heart valve assembly with the stent in thepartially collapsed state, compressing the valve assembly just prior toimplantation to a collapsed state having second diameter that is lessthan the first diameter, delivering the valve assembly to a native valvesite of a patient through the patient's vasculature, and expanding thevalve assembly at the native valve site to an expanded state having athird diameter that is greater than the first diameter.

In yet another representative embodiment, a prosthetic valve assemblycomprises a frame that is radially compressible to a compressed statefor percutaneous delivery of the valve assembly and radially expandableto an expanded state for operation of the valve assembly. The framecomprises first and second frame portions connected end-to-end, witheach frame portion comprising a plurality of circumferential strutsformed with multiple bends. The bends of the first frame portion haveangles that are less than the angles of the bends of the second frameportion when the frame is in the expanded state. A valve member can bemounted to the frame when the first frame portion is in an expandedstate and the second frame portion is in a partially collapsed state.For example, a base portion of the valve member can be attached to theexpanded first frame portion and the commissure tabs of the valve membercan be attached to the first and second frame portions.

In still another representative embodiment, a folding apparatus for usein mounting a prosthetic valve on a stent is configured to fold thevalve into an undulated shape having multiple angularly-spaced, radiallyextending folds and a diameter that is less than the diameter of theexpanded valve and stent.

The foregoing and other features and advantages of the invention willbecome more apparent from the following detailed description, whichproceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art prosthetic heart valveassembly configured for percutaneous introduction.

FIG. 2 is a perspective view of a percutaneous heart valve assemblyshown in a partially compressed state, according to one embodiment.

FIGS. 3A-3C show the frame of the heart valve assembly of FIG. 2 in apartially compressed state (FIG. 3A), an expanded state (FIG. 3B), and acompressed state (FIG. 3C).

FIG. 4 is a perspective view of the heart valve assembly of FIG. 2 shownprior to the valve member being mounted to the assembly.

FIG. 5 is a top plan view of the partially assembled valve assemblyshown in FIG. 4.

FIG. 6 is a plan view of an exemplary embodiment of a flexible skirtthat can be used to attach a valve member to a frame.

FIG. 7 is a plan view of another embodiment of a flexible skirt.

FIG. 8 is a top plan view of an exemplary embodiment of a foldingapparatus for use in assembling a valve assembly shown with a valvemember retained in a folded state and a frame placed around the foldedvalve member.

FIG. 9 is a perspective view of the folding apparatus.

FIG. 10 is a partially exploded, perspective view of the foldingapparatus shown with the housing removed.

FIG. 11 is a perspective view of the support plate, bases and associatedposts of the folding apparatus.

FIG. 12 is a top plan view of the folding apparatus shown with thehousing removed.

FIG. 13 is a side elevation view of a radially compressible andexpandable frame for a prosthetic valve assembly shown with an upperframe portion in a partially collapsed state and a lower frame portionin an expanded state, according to another embodiment.

FIG. 14 is a side elevation view of the frame of FIG. 13 shown with bothframe portions in expanded states.

FIG. 15 is a perspective view of a radially compressible and expandableframe shown with a first frame portion in a partially crimped condition,according to another embodiment.

DETAILED DESCRIPTION

As used herein, the singular forms “a,” “an,” and “the” refer to one ormore than one, unless the context clearly dictates otherwise.

As used herein, the term “includes” means “comprises.” For example, adevice that includes or comprises A and B contains A and B but mayoptionally contain C or other components other than A and B. A devicethat includes or comprises A or B may contain A or B or A and B, andoptionally one or more other components such as C.

As used herein, the “expanded” or “deployed” state of a valve assemblyor frame refers to the state of the valve assembly/frame when radiallyexpanded to its functional size. The “crimped” or “compressed” state ofa valve assembly or frame refers to the state of the valveassembly/frame when radially compressed to a diameter suitable fordelivering the valve assembly through a patient's vasculature on acatheter or equivalent mechanism. A valve assembly/frame that is“partially crimped” or “partially compressed” has a diameter that isless than the diameter of the valve assembly/frame in the expanded stateand greater than the diameter of the valve assembly/frame in thecompressed state. In particular embodiments, the diameter of thepartially crimped valve assembly is about two times greater than thecompressed diameter and the expanded diameter is about 1.5 times greaterthan the partially crimped diameter. In an exemplary embodiment, theexpanded diameter of the valve assembly is about 23 mm, the partiallycrimped diameter is about 15 mm, and the compressed diameter is about 7mm (about 22 French).

FIG. 2 shows a first embodiment of an expandable, percutaneousprosthetic heart valve assembly 100 in a partially collapsed or crimpedstate. The valve assembly 100 is suitable for crimping into a narrowconfiguration for positioning and expandable to a wider, deployedconfiguration so as to anchor the assembly in position at the desiredtarget location in the body (e.g., at the aortic annulus). The valveassembly 100 in the illustrated embodiment comprises a flexible valvemember 102 (also referred to herein in other embodiments as a valve)mounted on an expandable, annular support stent, or frame, 104. Thevalve member 102 is mounted to the frame 104 when the frame 104 is inthe partially collapsed state shown in FIG. 2. A flexible skirt 106 canbe situated between the outer surface of valve member 102 and the innersurface of the frame 104. The skirt 106 can be used to facilitatemounting of the valve member 102 to the frame 104, as described indetail below.

The frame 104 in the illustrated embodiment comprises a plurality ofangularly-spaced axial struts, or support members, 108 that extendaxially (longitudinally) of the frame and a plurality of support posts,or beams, 110 spaced in the illustrated example at 120-degree intervalsfrom each other around the frame 104. The support posts 110 can beformed with apertures 112 to facilitate mounting of the valve member 102to the posts 110 such as by suturing the valve member 102 to the posts.The frame 104 can also include a plurality of axially-spaced,circumferential bands, or struts, 114 attached to the axial struts 108and the support posts 110. The struts 114 are formed with multiple bendsthat allow the frame 104 to be crimped to a smaller diameter fordelivery to an implantation site and expanded to a larger diameter foranchoring the valve assembly at the implantation site. For example, eachof the struts 114 in the illustrated configuration includes a pluralityof linear strut members 116 a, 116 b arranged in a zig-zag or saw-toothconfiguration defining bends between adjacent strut members.

In alternative embodiments, the frame can have other configurations. Forexample, one or more of the circumferential bands 114 can have a curvedor serpentine shape rather than a zig-zag shape. Further, the frame 104can include various attachment elements (not shown), such as barbs,staples, flanges, and the like for enhancing the ability of the frame toanchor to the host tissue.

The frame 104 can be made from any of various suitable expandable and/orelastic materials and is typically made of a metal, such as stainlesssteel, titanium, or other biocompatible metals. The frame 104 also canbe made from a shape memory alloy such as nickel titanium (NiTi) shapememory alloys, as marketed, for example, under the trade name Nitinol.The skirt 106 can be made from any of various suitable biocompatiblesynthetic materials, such as woven polyester or polytetrafluoroethylene(PTFE).

The valve member 102 can have a leafed-valve configuration, such as thetricuspid valve configuration shown in the illustrated embodiment. Thevalve member 102 can be formed from three pieces of pliant materialconnected to each other at seams 118 (also referred to as commissuretabs) to form collapsible leaflets 122 and a base portion 120 (the lowerportion of the valve member in FIG. 2). The valve member 102 can beconnected to the skirt 106 at the base portion 120 of the valve memberand to the posts 110 at the seams 118. Various other valveconfigurations also can be used. Examples of other valves that can beutilized are disclosed in U.S. Pat. Nos. 6,730,118, 6,767,362, and6,908,481, which are incorporated herein by reference.

The valve member 102 can be made from biological matter, such as naturaltissue, pericardial tissue (such as bovine, porcine or equinepericardium), a harvested natural valve or other biological tissue.Alternatively, the valve member 102 can be made from biocompatiblepolymers or similar materials.

FIGS. 3A-3C are schematic views showing the frame 104 in the partiallycollapsed state (FIG. 3A) for mounting the valve member 102 (FIG. 2) tothe frame; a collapsed, or compressed, state (FIG. 3C) for deliveringthe valve assembly; and an expanded state (FIG. 3B) for anchoring thevalve assembly at an implantation site. As shown, when the valveassembly 100 is assembled, the frame 104 has an initial diameter D₁, andcan be crimped to a diameter D₂ that is less than D₁ and expanded to adiameter D₃ that is greater than D₁. In certain embodiments, forexample, the diameter D₁ of the partially collapsed frame 104 isapproximately twice the diameter D₂ of the collapsed frame and thediameter D₃ of the expanded frame is about 1.5 times greater than D₁. Inan exemplary embodiment, D₁ is about 15 mm, D₂ is about 7 mm, and D₃ isabout 23 mm. In certain embodiments, the frame 104 can be compressed toa diameter such that the strut members 116 a, 116 b are nearly verticaland parallel to axial struts 108.

In particular embodiments, the frame 104 is manufactured in thepartially collapsed state shown in FIG. 3A and need not be expanded orcollapsed prior to its attachment to the valve member 102. Initially,the strut members 116 a, 116 b define angles α₁ in the partiallycollapsed state and increase to angles α₂ when the frame is expanded.The angles α₁ defined between adjacent strut members 116 a, 116 b of thepartially collapsed frame are selected to allow for even and predictablecrimping of the frame, yet provide sufficient strength and rigidity tothe struts 114 when the frame is expanded to resist closing forcesexerted on the frame (for example, the recoil force exerted on the frameby the distorted stenosed native valve orifice). For example, in certainimplementations, the angles α₁ of the partially collapsed frame are inthe range of about 50 to about 90 degrees, with 70 degrees being aspecific example, and the angles α₂ of the expanded frame are in therange of about 90 to about 179 degrees, and more desirably in the rangeof about 90 to about 130 degrees, with 120 being a specific example.

As discussed above, known valve assemblies typically are assembled withthe frame in an expanded state. With the frame in the expanded state,the valve member can be expanded to closely conform to the inner surfaceof the frame, such as by mounting the valve member on a cylindricalmandrel having a diameter slightly smaller than the diameter of theexpanded frame. As a result, it is a relatively simple matter to attachthe valve member to the frame, such as with sutures. However, whenattaching the valve member 102 to the frame 104 in the partiallycollapsed state, the diameter of the valve member 102 can be muchgreater than the diameter D₁ of the partially collapsed frame 104. Thevalve member 102 in such cases cannot conform to the shape of thepartially collapsed frame, and as a result, assembly of the valveassembly is rendered more difficult. Accordingly, one or more of thefollowing techniques can be employed to facilitate the assembly process.

In one approach, for example, the flexible skirt 106 (FIGS. 2 and 4-6)is used as an attachment aid. When assembling the valve assembly 100,the skirt 106 is first attached to the inner surface of the frame 104,such as with sutures 130 or other suitable attachment techniques ormechanisms. The length of the skirt 106 (when laid flat) isapproximately equal to the inner circumference of the frame 104 whenexpanded. As best shown in FIG. 5, the skirt 106 therefore is attachedto the frame 104 at discrete, spaced-apart locations 134 around theperiphery of the skirt such that the skirt 106 takes on an undulatedshape with slack portions 138 between the connection locations remainingunattached to the frame. The spacing between the connection locations134 is such that when the frame 104 is expanded, the skirt takes on asubstantially tubular shape closely conforming in an abuttingrelationship with the inner surface of the frame. After attaching theskirt 106 to the frame 104, the base portion 120 of the valve member 102can then be attached to the skirt 106 and/or the support posts 110, suchas with sutures 132 (FIG. 2) or other suitable fasteners. The valvemember 102 is placed in a partially crimped state but when the frame 104is expanded, the base portion of the valve member expands to a tubularshape closely conforming to the inner surface of the skirt 106 in anabutting relationship.

As shown in FIG. 6, the skirt 106 (shown laid flat) can be provided withvisual indicia along its length to identify the locations on the skirtfor attaching the skirt to the frame 104. The visual indicia can be, forexample, markings 136, slits or holes formed in the skirt, or suturesattached at spaced-apart locations along the length of the skirt. Ifsutures are used to mark the connecting locations, the sutures can alsobe used in connecting the skirt to the frame.

FIG. 7 shows a skirt 150, according to another embodiment. The skirt 150is formed with a generally saw-tooth shaped edge 152 with apexes 154marking the locations along the length of the skirt for attaching theskirt to the frame 104.

In another approach for assembling the valve assembly 100, a foldingdevice can be utilized to fold or bend the valve member 102 into anundulated shape for attaching the valve member 102 to the frame 104.FIGS. 8-12 show an exemplary embodiment of a folding device, indicatedgenerally at 200. Referring to FIGS. 8 and 9, the folding device 200 inthe illustrated embodiment can comprise an outer housing, or casing,202, a plurality of fixed posts, or pins, 204, and a plurality ofmoveable posts, or pins, 206 extending from the housing 202. In thismanner, the housing serves as a base or support for the posts 204, 206.

There are a total of six fixed posts 204 and a total of six moveableposts 206 in the illustrated embodiment, although the number of posts204, 206 can vary in different applications. The fixed posts 204 can bemounted at fixed locations on the upper surface of the housing 202. Themoveable posts 206 are slidable in respective radially extending slots208 in the upper surface of the housing 202 so that the posts 206 can bemoved radially toward and away from each other. The posts 204, 206 areangularly spaced around a center point C on the base 202 centrallylocated between the posts. The center point C in the illustratedembodiment coincides with the geometric center of the housing 202,although in other embodiments the center point C can be offset from thegeometric center of the housing.

In use, the valve member 102 can be placed around the posts 204, 206with the valve member 102 extending around the outside of the fixedposts 204 and the inside of the moveable posts 206 (FIG. 8). The posts206 can then be moved radially inwardly toward each other to formmultiple angularly-spaced, radially extending folds 210 in the valvemember, as depicted in the FIG. 8. The folded valve member has adiameter (measured between diametrically opposing apexes 212) that isless than the diameter of the valve member in its expanded state. Thisallows the frame 104 (in the partially collapsed state) to be placedaround and attached to the valve member 102 at the apexes 212 of thefolds 210, such as by suturing the valve member to the frame at theapexes 212. As shown, the spacing between the fixed posts 204 and thecenter point C desirably is selected such that the partially collapsedframe 104 can contact the apexes 212 when placed around the folded valvemember. Slack portions 230 of the folded valve member between the apexes212 remain unattached to the frame 104. In certain embodiments, theapexes 212 of the folds are attached to the lower half of the frame 104at the base portion 120 of the valve member and to the support posts 110of the frame where the apexes 212 coincide with the seams of the valvemember. Thus, when the frame 104 is expanded to its functional size, thebase portion 120 of the valve member 102 expands to a tubular shapeclosely conforming to the inner surface of the frame in an abuttingrelationship.

The moveable posts 206 can be operatively connected to an adjustmentmechanism that is operable to move posts 206 simultaneously such thatthe posts 206 are always equidistant from the center point C. In thismanner, the folding device 200 can easily form substantially equal andsymmetrical folds 210 in the valve member 102 without having to positionindividual posts 206.

For example, referring to FIGS. 10-12, the illustrated folding device200 includes an adjustment mechanism 214 in the form of a circular platepositioned at the bottom of the folding device. The moveable posts 206are mounted to respective bases 216, which are supported on a supportplate 218 inside the housing 202. As shown in FIG. 11, each base 216 isprovided with a downwardly projecting pin 220, each of which extendsthrough a respective linear slot 222 formed in the support plate 218. Asbest shown in FIG. 12, the slots 222 are equally dispersed around thecenter point C of the device with each slot extending in a directionthat is offset from the center point C by the same distance. The bottomplate 214 is formed with a plurality of arcuate slots 224, each of whichreceives the bottom end portion of a respective pin 220 of a base 216.The slots 224 are equally dispersed around the center point C with thecenter of curvature of each slot 224 being offset from the center pointC by the same distance.

By virtue of the arrangement of the slots 208, 222, 224, rotation of thebottom plate 214 is effective to move the posts 206 simultaneouslytoward or away from each other. For example, referring to FIG. 12,rotating the bottom plate 214 counterclockwise causes the pins 220 tomove within their respective slots 222 (in the directions indicated byarrows 226), which in turn causes each base 216 to move in the samedirection. The bases 216 in turn move their respective pins 206 radiallyinwardly toward each other to create the folds 210 in the valve member102 (FIG. 8). Rotating the bottom plate 214 clockwise in FIG. 12 causesthe bases 216 to move in the opposite direction, which in turn causesthe posts 206 to move simultaneously radially outwardly from each other.

In another approach for assembling the valve assembly 100, the foldingdevice 200 can be used to fold the skirt 106, which can then be attachedto the frame 104 at the apexes of the folds contacting the frame. Theframe 104 and skirt 106 are then removed from the folding device and thevalve member 102 can be attached to the inner surface of the skirt 106.

In certain embodiments, the valve assembly 100 can be assembled prior tostorage. Just prior to implantation, the valve assembly is removed fromthe storage container, placed on the end portion of a delivery catheterand radially crimped about the catheter for percutaneous delivery.Alternatively, the components of the valve assembly can be storedseparately and assembled in the operating theater just prior toimplantation. A conventional crimping device can be used to crimp thevalve assembly on the catheter. One such crimping device is described inU.S. Pat. No. 6,730,118.

Various procedures can be employed for delivering and deploying thevalve assembly at a target site, as described for example in the '118patent. In one implementation, for example, the valve assembly ismounted on an inflatable balloon of a flexible catheter and insertedinto the patient's vasculature via an introducer sheath or othercannula. The valve assembly is advanced through the patient'svasculature while mounted on the balloon until it reaches the desiredtarget location (for example, at the aortic annulus in the case of anaortic valve assembly). The balloon is then inflated and the valveassembly expands radially, anchoring the frame to the surroundingtissue.

In another implementation, the frame 104 can be made of a self-expandingmaterial and the valve assembly can be mounted in a crimped state on theend of a catheter with a sheath over the valve assembly. The valveassembly is advanced through the patient's vasculature until it reachesthe desired target location, at which point the sheath is retracted fromthe valve assembly to allow the frame to expand and engage thesurrounding tissue. In another implementation, the valve assembly can beimplanted in an open-heart procedure with the valve assembly beingdelivered to the target site using a valve holder, as known in the art.

FIGS. 13 and 14 illustrate another embodiment of an expandable andcollapsible frame 300 of a heart valve assembly. FIG. 13 shows the frame300 in a partially collapsed state for mounting a valve member (e.g.,valve member 102). FIG. 14 shows the frame 300 expands to its functionalsize. The frame 300 includes a first frame portion 302 connectedend-to-end to a second frame portion 304. The valve member (not shown inthe drawings) is connected to the second frame portion 304, whichexhibits better crimpability than the first frame portion 302. The firstframe portion 302, on the other hand, has a more rigid construction thanthe second frame portion 304, and therefore enhances the overallstrength and rigidity of the frame 300. Prior to implantation, bothframe portions 302, 304 can be crimped to a smaller diameter from thepartially collapsed state shown in FIG. 13. When the valve assembly ispositioned at the target site in a patient, the frame portions 302, 304are expanded to their functional size, as shown in FIG. 14.

The first frame portion 302 includes a plurality of circumferential,zig-zag struts 306 connected to a plurality of axial struts 308. Thestruts 306 comprise a plurality of linear strut members 314 a, 314 b,with each adjacent pair of strut members connected to each other at anangle θ₁ in the expanded state (FIG. 14). Similarly, the second frameportion 304 includes a plurality of circumferential, zig-zag struts 310connected to a plurality of axial struts 312. The struts 310 comprise aplurality of linear strut members 316 a, 316 b, with each adjacent pairof strut members connected to each other at an angle θ₂.

The frame 300 is formed in the partially collapsed state (FIG. 13) withthe second frame portion 304 at its functional size and the first frameportion 302 having a frusto-conical shape tapering from a first diameterat the end connected to the second frame portion to a second, smallerdiameter at the opposite end. In this state, the second frame portion304 has an inner diameter approximately equal to the outer diameter ofthe valve member so that the valve member can be easily attached to thesecond frame portion 304 using conventional techniques or mechanisms.For example, the valve member can be sutured to the second frame portion304, similar to the valve assembly shown in FIG. 1.

Alternatively, the base portion of the valve member can be attached tothe second frame portion 304 around its circumference while thecommissure tabs can be attached to both the first and second frameportions. In this alternative embodiment, the frame 300 can have anoverall length (measured in the axial direction) that is approximatelyequal to or slightly greater than the valve member.

The angles θ₂ between strut members 316 a, 316 b are selected to permiteven and predictable crimping of the frame portion 304. In particularembodiments, for example, angles θ₂ are in the range of about 80 degreesto about 110 degrees, with 100 degrees being a specific example. In thismanner, the second frame portion 304 with the valve member mountedthereon can have a construction that is similar to the valve assemblyshown in FIG. 1.

The angles θ₁ between strut members 314 a, 314 b of the first frameportion 302 when expanded are greater than the angles θ₂, and inparticular embodiments the angles θ₁ are in the range of about 90degrees to about 130 degrees, with about 120 degrees being a specificexample. In this manner, the first frame portion 302 serves as theprimary structural component of the frame 300 to enhance the rigidity ofthe frame and better resist closing forces on the valve assembly once itis implanted. Due to the first frame portion 302 being in a partiallycrimped state when the valve member is attached (FIG. 13), it can bemore easily crimped to the fully crimped state for delivering the valveassembly through the patient's vasculature.

FIG. 15 illustrates another embodiment of an expandable and collapsibleframe 400 of a heart valve assembly. FIG. 15 shows the frame 400 in apartially collapsed state for mounting a valve member (e.g., valvemember 102). The frame 400 includes a first frame portion 402 connectedend-to-end to a second frame portion 404. The frame 400 is formed in thepartially collapsed state with the second frame portion 404 at itsexpanded, functional size, while the first frame portion 402 ispartially crimped and has a frusto-conical shape tapering from a firstdiameter at the end connected to the second frame portion to a second,smaller diameter at the opposite end. In this state, a valve member(e.g., valve member 102) can be attached to the first frame portion 402and/or the second frame portion 404, such as by suturing the valvemember to the frame.

The first frame portion 402 serves as the primary structural componentof the frame 400 and is generally more rigid than the second frameportion 404 once the frame is deployed. However, the geometry of thefirst frame portion 402 is generally less stable under crimping than thesecond frame portion 404 and therefore is formed in the partiallycrimped state shown in FIG. 15 so that it can be more easily crimped toa fully crimped state on a delivery catheter. In certain embodiments,the frame portions 402, 404 are constructed such that when both areexpanded, the struts of the first frame portion 402 have bends definingangles that are greater than the struts of the second frame portion 404.

The second frame portion 404 in the illustrated embodiment has aplurality of axially-spaced, circumferential struts 406, each of whichincludes a plurality of linear strut members 408 a, 408 b arranged in azig-zag or saw-tooth configuration defining angles ω₁ between adjacentstrut members. As shown, the second frame portion 404 in particularembodiments does not include axial or vertical strut members. Due to theabsence of axial strut members, this geometry is generally more stableand less susceptible to buckling during crimping. Consequently, thesecond frame portion 404 can be formed with obtuse angles ω₁ to enhancethe overall structural rigidity of the frame once implanted. Forexample, in exemplary embodiments, the angles ω₁ are in the range ofabout 91 degrees to about 110 degrees, with about 100 degrees being aspecific example. In alternative embodiments, however, the second frameportion 404 can be formed with angles ω₁ that are 90 degrees or less.

The first frame portion 402 in the illustrated embodiment comprises aplurality of generally ring-shaped structures or cells 410 connected toeach other at junctures 412 to form a circumferentially extending band.The first frame portion 402 can include angularly-spaced support posts,or beams, 414 spaced, for example, at 120-degree intervals from eachother around the frame. The support posts 414 can be formed withapertures 416 to facilitate mounting of a valve member to the posts 414such as by suturing the valve member to the posts. The lower end of eachpost 414 can be connected to the uppermost circumferential strut 406 ofthe second frame portion at the junction of two strut members 408 a, 408b to interconnect the first and second frame portions. The first frameportion 402 can also be interconnected to the second frame 404 by axialstrut members 418, each connected to and extending between a juncture412 and the uppermost circumferential strut 406 at the junction of twostrut members 408 a, 408 b.

Each cell 410 in the illustrated configuration is formed by first andsecond arcuate strut members 420 a, 420 b, respectively, that intersectat upper and lower junction points 422 a, 422 b, respectively. The strutmembers 420 a, 420 b of each cell 410 define first and second angles ω₂.When expanded to its functional size, the first frame portion 402expands radially to a generally cylindrical shape (indicated by thedashed outline in FIG. 15), causing the angles ω₂ to increase. Inparticular embodiments, the angles ω₂ of the first frame portion 402 inthe partially crimped state are in the range of about 70 degrees toabout 100 degrees, with 90 degrees being a specific example. When thefirst frame portion 402 is expanded to its functional size, the anglesω₂ between the strut members 420 a, 420 b are in the range of about 90degrees to about 130 degrees, with about 120 degrees being a specificexample.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

We claim:
 1. A percutaneous prosthetic heart valve assembly havingenhanced rigidity, comprising: a radially compressible and expandablesupport stent, the support stent having a compressed state with acompressed diameter for percutaneous delivery of the prosthetic heartvalve assembly to an implantation site, the support stent having anexpanded state with an expanded diameter for operation of the prostheticheart valve assembly at the implantation site, the support stent furtherhaving a partially collapsed state with a partially collapsed diameterthat is between the compressed and expanded diameters for attachment ofa valve member and storage of the assembly, the support stent formedwith a plurality of circumferential bands, each band comprising aplurality of linear strut members forming a zig-zag configuration,wherein when the support stent is in the partially collapsed stateadjacent strut members form angles of between about 50-90°, and in theexpanded state adjacent strut members form angles of about 90-179° forenhanced rigidity when the support stent is in the expanded state; and aflexible valve member coupled to the support stent in the partiallycollapsed state, wherein the valve member has an expanded configurationsuitable for functioning as a one-way valve with a correspondingdiameter that matches the expanded diameter of the support stent, andattaches at spaced locations within the support stent when the supportstent is in the partially collapsed state with locations therebetweenthat are out of contact with the stent.
 2. The prosthetic heart valveassembly of claim 1, further comprising a flexible skirt positionedbetween the support stent and the flexible valve member, wherein theskirt is sutured to the support stent and the valve member is sutured tothe skirt.
 3. A method for deploying the valve assembly of claim 1 at anative valve site of a patient, the method comprising: mounting theprosthetic heart valve assembly in the compressed state on a flexiblecatheter; guiding the catheter through the patient's vasculature to thenative valve site; and expanding the prosthetic heart valve assembly tocause the support stent to become anchored to the native valve site. 4.The prosthetic heart valve assembly of claim 2, wherein in the partiallycompressed state of the support stent, the flexible skirt includesmultiple angularly-spaced, radially extending folds having outer apicesthat are attached to the support stent.
 5. The prosthetic heart valveassembly of claim 2, wherein the flexible skirt has visual indiciamarking spaced attachment locations along the length of the skirt toindicate locations for attaching the skirt to the inner surface of thesupport stent.
 6. The prosthetic heart valve assembly of claim 5,wherein the visual indicia are selected from the group consisting of:markings, slits or apertures, sutures attached to the skirt, and alongitudinal edge of the skirt shaped to indicate the attachmentlocations.
 7. The prosthetic heart valve assembly of claim 5, whereinthe flexible skirt is formed with a generally saw-tooth shapedcircumferential edge to indicate the attachment locations.
 8. Theprosthetic heart valve assembly of claim 1, wherein the partiallycollapsed diameter is approximately mid-way between the compressed andexpanded diameters.
 9. The prosthetic heart valve assembly of claim 8,wherein the partially collapsed diameter is about two times thecompressed diameter, and the expanded diameter is about 1.5 times thepartially collapsed diameter.
 10. The prosthetic heart valve assembly ofclaim 9, wherein the expanded diameter is about 23 mm, the partiallycollapsed diameter is about 15 mm, and the compressed diameter is about7 mm.
 11. The prosthetic heart valve assembly of claim 1, wherein whenthe support stent is in the partially collapsed state the flexible valvemember is folded within the support stent so as to have an undulatingshape with outer fold apexes that contact and attach to the supportstent.
 12. The prosthetic heart valve assembly of claim 11, wherein thevalve member has slack portions between outer fold apexes that remainout of contact with the support stent, and wherein when the supportstent is expanded to the expanded state, the valve member assumes atubular cross-sectional profile within the support stent.
 13. Theprosthetic heart valve assembly of claim 1, wherein the support stent isballoon-expandable.
 14. The prosthetic heart valve assembly of claim 1,wherein the support stent is self-expandable.
 15. The prosthetic heartvalve assembly of claim 1, wherein the support stent further comprises aplurality of support beams spaced at about 120-degree intervals fromeach other around the support stent and connected to each of thecircumferential bands, the support beams being formed with apertures tomount the flexible valve member by suturing to the beams.
 16. Theprosthetic heart valve assembly of claim 1, wherein the support stentcomprises a first frame portion connected end-to-end to a second frameportion, and the flexible valve member is connected to the second frameportion, wherein the first frame portion has a more rigid constructionthan the second frame portion.
 17. The prosthetic heart valve assemblyof claim 1, wherein when the support stent is in the partially collapsedstate, adjacent strut members form angles that render thecircumferential bands nearly circular.
 18. A percutaneous prostheticheart valve assembly comprising: a frame that is radially compressibleto a compressed state for percutaneous delivery of the valve assemblyand radially expandable to an expanded state for operation of the valveassembly at the implantation site, the frame comprising first and secondframe portions connected end-to-end, each frame portion comprising aplurality of circumferential struts, each strut formed with multiplebends, and a flexible valve member connected to the second frameportion, and wherein the frame has a partially collapsed state with thefirst frame portion having a partially collapsed diameter that isbetween the diameters of the first frame portion in its compressed andexpanded states and where the second frame portion is in its expandedstate having an inner diameter approximately equal to an outer diameterof the valve member, and in the partially collapsed state of the framethe bends of the first frame portion having angles θ₁ that are less thanangles θ₂ of the bends of the second frame portion.
 19. The prostheticheart valve assembly of claim 18, wherein in the partially collapsedstate of the frame the first frame portion has a frusto-conical shapetapering from a first diameter at an end connected to the second frameportion to a second, smaller diameter at the opposite end.
 20. Theprosthetic heart valve assembly of claim 18, wherein in the partiallycollapsed state the second, smaller diameter of the first frame portionis approximately mid-way between the compressed and expanded diametersof the frame.
 21. The prosthetic heart valve assembly of claim 18,wherein the first frame portion has a more rigid construction than thesecond frame portion.
 22. The prosthetic heart valve assembly of claim18, wherein 90 degrees <θ₁ <179 degrees.
 23. The prosthetic heart valveassembly of claim 18, further comprising a flexible skirt positionedbetween the second frame portion and the flexible valve member, whereinthe skirt is sutured to the second frame portion and the valve member issutured to the skirt.
 24. The prosthetic heart valve assembly of claim18, wherein the frame is balloon-expandable.
 25. The prosthetic heartvalve assembly of claim 18, wherein the frame is self-expandable. 26.The prosthetic heart valve assembly of claim 18, wherein the secondframe portion further comprises a plurality of support beams spaced atabout 120-degree intervals from each other around the second frameportion and connected to each of the circumferential struts, the supportbeams being formed with apertures to mount the flexible valve member bysuturing to the beams.